Legal expert: Robert Mueller's Russia probe may be a bust because he was illegally appointed

Paul Manafort and Richard Gates have pleaded not guilty to all charges in Robert Mueller’s Russia probe, but at least one legal scholar has suggested special counsel Robert Mueller’s investigation may not be constitutional.

According to the reasoning, one of the key factors is how Mueller's role is structured. Jeff Sessions recused himself, and Deputy Attorney General Rod Rosenstein has said Mueller doesn’t report to him with day-to-day decisions.

Because of that, Pepperdine University law professor Douglas W. Kmiec says that Mueller effectively does not have a supervisor — and without one, the Senate would have to confirm Mueller as an executive appointee. Otherwise, his appointment is unconstitutional.

In an op-ed for the Los Angeles Times penned in July, Kmiec suggested that — with Comey’s alleged assumption that President Trump is a wrongdoer— and the special counsel process labelling him as such, that “the investigation itself is arguably equivalent to an unconstitutional indictment.”

23PHOTOS

Former FBI Director Robert Mueller

See Gallery

Former FBI Director Robert Mueller

WASHINGTON, DC - OCTOBER 28: Former FBI director Robert Mueller attends the ceremonial swearing-in of FBI Director James Comey at the FBI Headquarters October 28, 2013 in Washington, DC. Comey was officially sworn in as director of FBI on September 4 to succeed Mueller who had served as director for 12 years. (Photo by Alex Wong/Getty Images)

US President Barack Obama applauds outgoing Federal Bureau of Investigations (FBI) director Robert Mueller (L) in the Rose Garden at the White House in Washington on June 21, 2013 as he nominates Jim Comey to be the next FBI director. Comey, a deputy attorney general under George W. Bush, would replace Mueller, who is stepping down from the agency he has led since the week before the September 11, 2001 attacks. AFP PHOTO/Nicholas KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)

Outgoing FBI Director Robert Mueller applauds key staff members during a farewell ceremony held for him at the Justice Department in Washington, August 1, 2013. On Monday the U.S. Senate confirmed former Deputy Attorney General James Comey to replace Mueller, who has led the bureau since shortly before the September 11, 2001, attacks on the United States. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS CRIME LAW HEADSHOT)

391489 03: U.S. President George W. Bush speaks during a conference as he stands with Justice Department veteran Robert Mueller, left, who he has nominated to head the FBI, and Attorney General John Ashcroft July 5, 2001 the Rose Garden at the White House in Washington, DC. (Photo by Mark Wilson/Getty Images)

Outgoing FBI Director Robert Mueller stands for the national anthem during a farewell ceremony for him at the Justice Department in Washington, August 1, 2013. On Monday the U.S. Senate confirmed former Deputy Attorney General James Comey to replace Mueller, who has led the bureau since shortly before the September 11, 2001, attacks on the United States. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS CRIME LAW)

Outgoing FBI Director Robert Mueller (L) reacts to a standing ovation from the audience, Deputy U.S. Attorney General James Cole (C) and U.S. Attorney General Eric Holder (R) during Mueller's farewell ceremony at the Justice Department in Washington, August 1, 2013. On Monday the U.S. Senate confirmed former Deputy Attorney General James Comey to replace Mueller, who has led the bureau since shortly before the September 11, 2001, attacks on the United States. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS CRIME LAW)

Outgoing FBI Director Robert Mueller gestures during his remarks at a farewell ceremony held for him at the Justice Department in Washington, August 1, 2013. On Monday the U.S. Senate confirmed former Deputy Attorney General James Comey to replace Mueller, who has led the bureau since shortly before the September 11, 2001, attacks on the United States. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS CRIME LAW)

FILE PHOTO -- U.S. Attorney General John Ashcroft (R) and FBI Director Robert Mueller speak about possible terrorist threats against the United States, in Washington, May 26, 2004. REUTERS/Kevin Lamarque/File Photo

Outgoing FBI Director Robert Mueller reacts to applause from the audience during his farewell ceremony at the Justice Department in Washington, August 1, 2013. On Monday the U.S. Senate confirmed former Deputy Attorney General James Comey to replace Mueller, who has led the bureau since shortly before the September 11, 2001, attacks on the United States. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS CRIME LAW)

UNITED STATES - JUNE 19: Chairman Pat Leahy, D-Vt., right, and FBI Director Robert Mueller make their way to a Senate Judiciary Committee hearing in Dirksen Building on oversight of the FBI. (Photo By Tom Williams/CQ Roll Call)

Outgoing FBI Director Robert Mueller (C) delivers remarks at a farewell ceremony for him at the Justice Department in Washington, August 1, 2013. On Monday the U.S. Senate confirmed former Deputy Attorney General James Comey to replace Mueller, who has led the bureau since shortly before the September 11, 2001, attacks on the United States. Also onstage with Mueller are Deputy U.S. Attorney General James Cole (FROM L), U.S. Attorney General Eric Holder, former CIA Director George Tenet and TSA Administrator John Pistole. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS CRIME LAW)

WASHINGTON, DC - MAY 15: (L-R) Rep. Steny Hoyer (D-MD), U.S. Attorney General Eric Holder, Homeland Security Secretary Janet Napolitano, FBI Director Robert Mueller and Immigration and Customs Enforcement Director John Morton attend the National Peace Officers' Memorial Service at the U.S. Capitol May 15, 2013 in Washington, DC. Holder and other members of the Obama administration are being criticized over reports of the Internal Revenue Services' scrutiny of conservative organization's tax exemption requests and the subpoena of two months worth of Associated Press journalists' phone records. (Photo by Chip Somodevilla/Getty Images)

FBI Director Robert Mueller testifies before the House Judiciary Committee hearing on Federal Bureau of Investigation oversight on Capitol Hill in Washington June 13, 2013. Mueller said on Thursday that the U.S. government is doing everything it can to hold confessed leaker Edward Snowden accountable for splashing surveillance secrets across the pages of newspapers worldwide. REUTERS/Yuri Gripas (UNITED STATES - Tags: POLITICS CRIME LAW)

FBI Director Robert Mueller (L) arrives for the Obama presidential inauguration on the West Front of the U.S. Capitol January 21, 2013 in Washington. President Barack Obama was re-elected for a second term as President of the United States. Woman at right is unidentified. REUTERS/Win McNamee-POOL (UNITED STATES)

WASHINGTON, : FBI Director Robert Mueller answers questions before Congress 17 October 2002 on Capitol Hill in Washington. Mueller was testifying before the House and Senate Select Intelligence committees' final open hearing investigating events leading up to the September 11, 2001. AFP Photos/Stephen JAFFE (Photo credit should read STEPHEN JAFFE/AFP/Getty Images)

399994 02: Federal Bureau of Investigation (FBI) Director Robert Mueller visits the American military compound at Kandahar Airport January 23, 2002 in Kandahar, Afghanistan. Mueller had lunch with FBI officials and Haji Gulali, commander of the Kandahar region. (Photo by Mario Tama/Getty Images)

Federal Bureau of Investigation (FBI) Director Robert Mueller (L) stand during the National Anthem alongside Attorney General Eric Holder (R) and Deputy Attorney General James Cole (C) during a farewell ceremony in Mueller's honor at the Department of Justice on August 1, 2013. Mueller is retiring from the FBI after 12-years as Director. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)

399994 01: Federal Bureau of Investigation (FBI) Director Robert Mueller greets American forces on the American military compound at Kandahar Airport January 23, 2002 in Kandahar, Afghanistan. Mueller had lunch with FBI officials and Haji Gulali, commander of the Kandahar region. (Photo by Mario Tama/Getty Images)

UNITED STATES - JUNE 19: FBI Director Robert Mueller, center, talks with Chairman Pat Leahy, D-Vt., right, and Sen. Orrin Hatch, R-Utah, talk before a Senate Judiciary Committee hearing in Dirksen Building on oversight of the FBI. (Photo By Tom Williams/CQ Roll Call)